Oerhaul the Vendor import/export between Rattail and CORE

also, add new DB schema specific to this integration, to hold PKs etc.

rattail_corepos/importing/model.py

@@ -0,0 +1,39 @@
+# -*- coding: utf-8; -*-
+################################################################################
+#
+#  Rattail -- Retail Software Framework
+#  Copyright © 2010-2020 Lance Edgar
+#
+#  This file is part of Rattail.
+#
+#  Rattail is free software: you can redistribute it and/or modify it under the
+#  terms of the GNU General Public License as published by the Free Software
+#  Foundation, either version 3 of the License, or (at your option) any later
+#  version.
+#
+#  Rattail is distributed in the hope that it will be useful, but WITHOUT ANY
+#  WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+#  FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more
+#  details.
+#
+#  You should have received a copy of the GNU General Public License along with
+#  Rattail.  If not, see <http://www.gnu.org/licenses/>.
+#
+################################################################################
+"""
+Rattail model importer extensions, for CORE-POS integration
+"""
+
+from rattail import importing
+
+
+##############################
+# core importer overrides
+##############################
+
+class VendorImporter(importing.model.VendorImporter):
+
+    extension_attr = '_corepos'
+    extension_fields = [
+        'corepos_id',
+    ]